Inhibiting phase separation in low viscosity water-based pesticide suspensions

ABSTRACT

The present invention provides a composition for inhibiting phase separation and the resulting non-uniform distribution of an active ingredient in low viscosity, water-based pesticide suspensions. In accordance with this invention, the composition comprises from about 0.003% to about 50% by weight of a pesticide, from about 0.5% to about 10% by weight of a wetting agent; from about 0.0% to about 0.8% by weight of a thickener; from about 0.1% to about 0.5% of an antimicrobial agent; from about 5% to about 20% of an anti-freeze; from about 1% to about 8% of a hydrophobic fumed silica; and from about 40% to about 95% of water. In an embodiment of the invention, the hydrophobic fumed silica results from a hydrophilic silica which is treated with dimethyldichlorosilane.

[0001] This application is a continuation-in-part of U.S. applicationSer. No. 09/506,655, filed on Feb. 17, 2000, which is acontinuation-in-part of U.S. application Ser. No. 09/228,904, filed onJan. 11, 1999 (now U.S. Pat. No. 6,074,987), which is a CIP of U.S.application Ser. No. 09/086,075, filed on May 28, 1998 (now abandoned).

TECHNICAL FIELD OF THE INVENTION

[0002] The present invention relates to a composition for inhibitingphase separation and the resulting non-uniform distribution of an activeingredient in low viscosity, water-based pesticide suspensions. Moreparticularly, the composition of the present invention comprises ahydrophobic fumed silica to inhibit phase separation and the resultingnon-uniform distribution of an active ingredient in the low-viscosity,water-based pesticide suspension. The preferred hydrophobic fumed silicaresults from a hydrophilic silica which is treated withdimethyidichlorosilane.

BACKGROUND OF THE INVENTION

[0003] A pesticide suspension is a homogeneous mixture of small solidparticles of pesticide suspended in a liquid medium. During periods ofnon-agitation, the solid particles with a density greater than thedensity of the liquid medium will settle toward the bottom of thecontainer and homogeneity is not maintained. Similarly, solid particleswith a density less than the density of the liquid medium will settletoward the top of the container and homogeneity is not maintained. Theloss of homogeneity can cause product failure if it results innon-uniform applications of the pesticide, and plugging of strainers andnozzles used with application equipment. In practice, the usual ways toinhibit settling of the particles include (i) making the density of theliquid medium as close as possible to that of the solid pesticide,and/or (ii) building high viscosity into the suspension. Changing thedensity of the liquid medium is usually not feasible, and building highviscosity into the suspension causes problems in the production,handling and performance of the pesticide.

[0004] Therefore, the practice of combining or formulating the pesticidecompounds with inert ingredients to facilitate their dispersibility inwater, has developed. Such water dispersible formulations have generallybeen prepared by combining the pesticide with (i) an emulsifier orwetting agent, (ii) a dispersant, and (iii) an inert carrier or fillermaterial. The inert carrier or filler material has been found necessaryin order to obtain a suitable admixture of the emulsifier, dispersantand pesticide, and to facilitate the size reduction of these ingredientsto an appropriate particle size. The inert carrier or filler materialmay be either a solid or a liquid. The former type of formulationsinclude wettable powders such as those discussed in U.S. Pat. No.3,737,551. Other types of solid formulations such as the waterdispersible granules of U.S. Pat. No. 3,920,442, have been proposed. Thelatter type of formulations include flowables in which the majordispersing medium is water, such as those disclosed in U.S. Pat. No.3,060,084

[0005] The disadvantages of these formulations known in the art includedifficulty in handling when preparing the suspensions, a tendency tocake during storage, and extreme sensitivity to high temperature. Thus,there has long been a need in the art for a flowable aqueous pesticidecomposition which is easily handled during preparation and use, whichhas excellent shelf-life even during extended storage and which iscompletely dispersible in water.

SUMMARY OF THE INVENTION

[0006] It is an object of the present invention to provide a compositionfor inhibiting phase separation and the resulting non-uniformdistribution of an active ingredient in low viscosity, water-basedpesticide suspensions. The composition contains from about 0.003% toabout 50% by weight of a pesticide; from about 0.5% to about 10% byweight of a wetting agent; from about 0.0% to about 0.8% by weight of athickener; from about 0.1% to about 0.5% of an antimicrobial agent; fromabout 5% to about 20% of an anti-freeze; from about 1% to about 8% of ahydrophobic fumed silica; and from about 40% to about 95% of water.

[0007] It is also an object of the present invention to provide acomposition for inhibiting phase separation and the resultingnon-uniform distribution of an active ingredient in low viscosity,water-based pesticide suspensions without changing the density of theliquid medium and/or building high viscosity into the suspension.

[0008] These and other objects that will be apparent to those skilled inthe art are accomplished by adding hydrophobic fumed silica to thelow-viscosity, water-based pesticide suspension. The preferredhydrophobic fumed silica results from a hydrophilic silica which istreated with dimethyldichlorosilane.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

[0009] The composition of the present invention comprises a combinationof a low viscosity water-based pesticide formulation and hydrophobicfumed silica. In an embodiment of the present invention, “low viscosity”is defined as a viscosity of less than about 900 cps. The pesticideformulation includes a pesticides a wetting agent; a thickener; anantimicrobial agent; an antifreeze agent; and water.

[0010] In an embodiment of the present Invention, the pesticidedemonstrates the following properties; a friable solid pesticide whichis capable of being fractured or shattered into small particles, whichhas a melting point of less than about 60° C., and a water solubility ofno more than about 1000 ppm at a temperature of about 40° C. Further,the pesticide is resistant to Ostwald ripening and its resulting crystalgrowth. Moreover, the pesticide is not easily hydrolyzed or degraded byan aqueous environment.

[0011] The pesticide of the present invention is selected from the groupconsisting of an insecticide, a fungicide, and a herbicide.Substantially any insecticide, fungicide or herbicide known in the artmay be used. Preferred insecticides include the heterocyclic compoundsdescribed in U.S. Pat. Nos. 6,022,871; 5,852,012; 5,719,146; 5,034,404;4,849,432; 4,742,060; and RE 35,811, the disclosures of which are hereinincorporated by reference. In a particularly preferred embodiment of theinvention, the insecticide is a chloronicotinyl or a chlorothiazole.Moreover, insecticides of the following general formulas (I), (II),(III) and (IV) are most preferred.

[0012] A preferred fungicide is tebuconazole, and a preferred herbicideis metribuzin.

[0013] Wetting agents serve to reduce the surface tension at thewater-solid interface and therefore, increase the tendency of the waterto contact the complete surface of the active ingredient particles. Bothanionic and nonionic surfactants are useful. Examples of anionicsurfactants include alkyl polyether alcohol sulfates, arylalkylpolyether alcohol sulfates, arylalkyl sulfonates, alkyinaphthalenesulfonates, and alkyl phenoxybenzene disulfonates. Nonionic surfactantsinclude arylalkyl polyether alcohols, aklyl polyether alcohols,polyoxyethylene fatty acid esters, polyethylene sorbitan fatty acidesters, polyalkylene oxide block copolymers, polyalkylene oxide blockcopolymer monohydric alcohols and polyalkylene oxide block copolymeralkyl phenols. Preferred wetting agents include sodium naphthaleneformaldehyde condensate and ethoxylated polyoxypropylene.

[0014] A thickener is generally a water soluble or water dispersibleanionic colloid possessing shear thinning properties, low sensitivity totemperature, good stability in both acidic and basic media, andcompatibility with most inorganic materials. Examples of thickeningagents include polysaccharide gums such as xanthan gum, guar gum, gumarabic; organically modified montmorillonite clays, attapulgite clays,carboxy-vinyl copolymers, and cellulose ethers. Preferred thickenersinclude xanthan gum and hydroxypropyl methylcellulose.

[0015] An antimicrobial agent is generally used to prevent the growth ofbacteria, fungi, or other microbial organisms that can flourish in anaqueous environment. Examples of antimicrobial agents include1,2-benzisothiazolin-3-one, methyl or propyl parahydroxybenzoate,2-bromo-2-nitro-propane-1,2-diol, sodium benzoate, glutaraldehyde,O-phenylphenol, 5-chloro-2-methyl-4-isothiazolin-3-one,pentachlorophenol, 2,4-dichloro-benzyl alcohol, andbenzisothiazolinones. Preferred antimicrobial agents include1,2-benzisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one plus,5-chloro-2-methyl-4-isothiazolin-3-one.

[0016] An anti-freeze agent (freeze point depressant) includesrelatively low molecular weight aliphatic alcohols such as ethyleneglycol, propylene glycol, glycerine, hexane diol, and sorbitol.Preferred anti-freeze agents include dipropylene glycol, glycerine,hexylene glycol, and propylene glycol.

[0017] Hydrophobic fumed silicas are made by treating the surface ofhydrophilic fumed silicas with a substance that chemically bonds and,thereby, changes the surface from one that is easily wetted by water toone that adsorbs hardly any water (even at high levels of atmosphericmoisture). The preferred hydrophobic fumed silica of the presentinvention comprises a hydrophilic fumed amorphous silica treated withdimethyidichlorosilane.

[0018] The composition of the pesticide suspension of the presentinvention is generally as follows. Weight % Pesticide 0.003-50   WettingAgent 0.5-10  Thickener 0.0-0.8 Antimicrobial Agent 0.1-0.5 Anti-Freeze 5-20 Hydrophobic Fumed Silica 1-8 Water 40-95

[0019] The composition of the present invention contains from about0.003% to about 50% by weight of a pesticide; from about 0.5% to about10% by weight of a wetting agent; from about 0.0% to about 0.8% byweight of a thickener; from about 0.1% to about 0.5% of an antimicrobialagent; from about 5% to about 20% of an anti-freeze; from about 1% toabout 8% of a hydrophobic fumed silica; and from about 40% to about 95%of water.

[0020] Having thus described our invention, the following examples aregiven as being illustrative thereof. All weights and percentages givenare parts by weight or percentages by weight, unless otherwiseindicated.

EXAMPLES

[0021] Example 1

[0022] A study was conducted to demonstrate the effectiveness of 0.5% to7.0% hydrophobic amorphous fumed silica in reducing the settling rate ofa water-based suspension concentrate (SC) containing 0.5 poundimidacloprid insecticide per gallon.

[0023] [A.] SC Concentrate with 0% Hydrophobic Fumed Silica

[0024] Blended together and homogenized by means of a Ross high-shearmixer were 152 grams of sodium naphthalene formaldehyde condensate(wetting agent), 152 grams of ethoxylated polyoxypropylene (wettingagent), 38 grams of a 19% solution of 1,2-benzisothiazolin-3-one inaqueous dipropylene glycol (antimicrobial agent), 14 grams of xanthangum (thickener), 759 grams of glycerine (anti-freeze) and 4856 grams ofdeionized water. A suspension containing 0.5 pound imidaclopridinsecticide per gallon was prepared by blending 5962 grams of thismixture with 2139 grams ADMIRE 2, a water-based suspension concentratecontaining 2 pounds imidacloprid insecticide per gallon manufactured byBayer Corporation, and mixed to uniformity with a low-shear paddlemixer. The final make-up of the suspension was then 5.6% imidaclopridinsecticide, 2.4% sodium naphthalene formaldehyde condensate, 2.4%ethoxylated polyoxypropylene, 0.5% 1,2-benziso-thiazolin-3-one solution,0.2% xanthan gum, 12.0% glycerine, and 76.9% water.

[0025] [B.] SC Concentrate with 0.5% Hydrophobic Fumed Silica

[0026] The composition as described in [A.] was used with the followingnoted exceptions, (i) 4815 grams of deionized water were used in thecomposition, (ii) 40 grams of hydrophobic fumed silica resulting fromdimethyidichlorosilane treated hydrophilic fumed silica were added tothe composition and homogeneously dispersed with the Ross high-shearmixer, and (iii) the final make-up of the suspension contained 76.4%water, and 0.5% hydrophobic silica.

[0027] [C.] SC Concentrate with 1.0% Hydrophobic Fumed Silica

[0028] The composition as described in [B.] was used with the followingnoted exceptions, (i) 4775 grams of deionized water were used, (ii) 81grams of hydrophobic fumed silica resulting from dimethyidichlorosilanetreated hydrophilic fumed silica were added, and (iii) the final make-upof the suspension contained 75.9% water, and 1.0% hydrophobic silica.

[0029] [D.] SC Concentrate with 4.0% Hydrophobic Fumed Silica

[0030] The composition as described in [C.] was used with the followingnoted exceptions, (i) 4532 grams of deionized water were used, (ii) 324grams of hydrophobic fumed silica resulting from dimethyldichlorosilanetreated hydrophilic fumed silica were added, and (iii) the final make-upof the suspension contained 72.9% water, and 4.0% hydrophobic silica.

[0031] [E.] SC Concentrate with 6.0% Hydrophobic Fumed Silica

[0032] The composition as described in [D.] was used with the followingnoted exceptions, (i) 4369 grams of deionized water were used, (ii) 486grams of hydrophobic fumed silica resulting from dimethyldichlorosilanetreated hydrophilic fumed silica were added, and (iii) the final make-upof the suspension contained 70.9% water, and 6.0% hydrophobic silica.

[0033] [F.] SC Concentrate with 7.0% Hydrophobic Fumed Silica

[0034] The composition as described in [E.] was used with the followingnoted exceptions, (i) 4289 grams of deionized water were used, (ii) 567grams of hydrophobic fumed silica resulting from dimethyldichlorosilanetreated hydrophilic fumed silica were added, and (iii) the final make-upof the suspension contained 69.9% water, and 7.0% hydrophobic silica.

[0035] Each of these six suspensions was then stored at 50° C. for 56days in a 1-quart clear glass jar with a lid. Storage at 50° C.increases the rate of chemical decomposition and physical degradation asopposed to storage at room temperature or below. After 3 days ofstorage, the settling of solid insecticide particles in the suspensionwith 0% hydrophobic silica resulted in the top 40% of the suspensionbeing a clear liquid (syneresis); storage for 21 days resulted insettling that left the top 70% of the suspension a clear liquid. Theaddition of 0.5% to 7.0% hydrophobic amorphous fumed silicasignificantly reduced the settling rates. The results are shown inTable 1. TABLE 1 WATER-BASED SUSPENSION CONTAINING 0.5 POUNDIMIDACLOPRID INSECTICIDE PER GALLON AND 0.5% TO 7.0% HYDROPHOBIC FUMEDSILICA Hydrophobic Syneresis, % Amorphous Viscosity* 3 days 21 days 28days 56 days Silica, % cps, 20° C. 50° C. 50° C. 50° C. 50° C. 0 200 4070 — — 0.5 200 5 20 — — 1.0 200 5 10 34 59 4.0 250 6 6  6 12 6.0 260 <12 — — 7.0 350 <1 1 — —

[0036] Example 2

[0037] A study was conducted to compare the effectiveness of 0.5%hydrophobic amorphous silica with that of 0.5% hydrophilic silica inreducing the settling rate of suspensions containing 0.5 pound pergallon of (i) imidacloprid insecticide, (ii) metribuzin herbicide, or(iii) tebuconazole fungicide.

[0038] [A.] Imidacloprid Suspension with 0.5% Hydrophobic Fumed Silica

[0039] Blended together and homogenized by means of a Ross high-shearmixer, were 56 grams of Morwet D-425 (sodium naphthalene formaldehydecondensate; wetting agent), 56 grams Witconol 324 (ethoxylatedpolyoxypropylene; wetting agent), 14 grams Proxel GXL (a 19% solution of1,2-benzisothiazolin-3-one in aqueous dipropylene glycol; antimicrobialagent), 5 grams Rhodopol 50 MD (xanthan gum; thickener), 280 gramsglycerine (anti-freeze), and 1789 grams deionized water. Then 15 gramsof Aerosil R-972 (hydrophobic fumed silica resulting fromdimethyidichlorosilane treated hydrophilic fumed silica) was added andhomogeneously dispersed with the Ross high-shear mixer. A suspensioncontaining 0.5 pound imidacloprid per gallon was prepared by blending294 grams of this mixture with 106 grams ADMIRE 2, and mixed touniformity with a low-shear paddle mixer. The final concentration ofimidacloprid in the suspension was 5.6%; the concentration ofhydrophobic silica was 0.5%.

[0040] [B.] Imidacloprid Suspension with 0.5% Hydrophilic Fumed Silica

[0041] The composition as described in [A.] was used with the followingexception, 15 grams of Aerosil 200 (hydrophilic fumed silica) were addedto the [B.] mixture instead of the Aerosil R-972 (hydrophobic fumedsilica) which was added to the [A.] mixture.

[0042] [C.] Metribuzin Suspension with 0.5% Hydrophobic Fumed Silica

[0043] The composition as described in [A.] was used with the followingexception, a metribuzin suspension, instead of an imidaclopridsuspension was used. In [C.], a suspension containing 0.5 poundmetribuzin per gallon was prepared by blending 368 grams of this mixturewith 32 grams SENCOR 70 WP, a wettable powder containing 70% metribuzinherbicide manufactured by Bayer Corporation, and mixed to uniformitywith a low-shear paddle mixer. The final concentration of metribuzin inthe suspension was 5.6%; the concentration of hydrophobic silica was0.5%.

[0044] [D.] Metribuzin Suspension with 0.5% Hydrophilic Fumed Silica

[0045] The composition as described in [C.] was used with the followingexception, 15 grams of Aerosil 200 (hydrophilic fumed silica) were addedto the [D.] mixture instead of the Aerosil R-972 (hydrophobic fumedsilica) which was added to the [C.] mixture.

[0046] [E.] Tebuconazole Suspension with 0.5% Hydrophobic Fumed Silica

[0047] The composition as described in [A.] was used with the followingexception, a tebuconazole suspension, instead of an imidaclopridsuspension was used. In [E.], a suspension containing 0.5 poundtebuconazole per gallon was prepared by blending 342 grams of thismixture with 58 grams FOLICUR 3.6, a water-based suspension concentratecontaining 3.6 pounds tebuconazole fungicide per gallon manufactured byBayer Corporation, and mixed to uniformity with a low-shear paddlemixer. The final concentration of tebuconazole in the suspension was5.6%; the concentration of hydrophobic silica was 0.5%.

[0048] [F.] Tebuconazole Suspension with 0.5% Hydrophilic Fumed Silica

[0049] The composition as described in [E.] was used with the followingexception, 15 grams of Aerosil 200 (hydrophilic fumed silica) were addedto the [F.] mixture instead of the Aerosil R-972 (hydrophobic fumedsilica) which was added to the [E.] mixture.

[0050] Each of these six suspensions was stored at 50° C. for 21 days ina 1-quart clear glass jar with a lid. The results of these storage testsare shown in Tables 2, 3, and 4.

[0051] Table 2 indicates that during the 21 day storage period, thehydrophobic silica, Aerosil R-972, was significantly more effective inreducing syneresis in the metribuzin and tebuconazole suspensions thanthe hydrophilic silica, Aerosil 200, or no silica. The syneresisreduction in the imidacloprid suspension was similarly significant for10 days storage. However, the similarities of the effectiveness of 0.5%hydrophobic silica, 0.5% hydrophilic silica, and 0% silica at 14 and 21days was attributed to this particular imidacloprid suspension needingmore than 0.5% silica to show significant differences. For confirmationpurposes, a follow-up study was conducted and the results are shown inTable 5.

[0052] Table 3 shows that the use of the hydrophobic silica achievedreduced syneresis without resulting in high viscosities either before orafter storage.

[0053] Table 4 shows the use of hydrophobic silica achieved reducedsyneresis without resulting in sediment that was difficult to dispersefollowing storage.

[0054] Table 5 shows the results of storage of PREMISE 0.5 SC(Imidicloprid) suspensions containing 0.5% -1.0% hydrophilic silica(Aerosil 200) and 0.5% to 4.0% hydrophobic silica (Aerosil R-972). Allsuspensions were made using the materials and processes used to make thePREMISE 0.5 SC for the study reported in Table 2. The data shows that atconcentrations of 0.5% silica or greater, the hydrophobic silica issignificantly more effective in reducing syneresis than the hydrophilicsilica. TABLE 2 % SYNERESIS AFTER STORAGE AT 50° C. SENCOR 0.5 SC(METRIBUZIN) FOLICUR 0.5 SC (TEBUCONAZOLE) PREMISE 0.5 SC (IMIDACLOPRID)0.5% 0.5% 0.5% 0.5% 0.5% 0.5% Aerosil R972 Aerosil 200 Aerosil R972Aerosil 200 Aerosil R972 Aerosil 200 (Hydro- (Hydro- 0.0% (Hydro-(Hydro- 0.0% (Hydro- (Hydro- 0.0% TEST phobic) philic) Aerosil phobic)philic) Aerosil phobic) philic) Aerosil  3 days 3 28 46 11 21 37 5 20 4010 days 5 51 59 20 60 66 20 40 50 14 days 10 68 69 31 61 84 50 60 60 21days 14 69 69 41 64 87 52 no data 66

[0055] TABLE 3 VISCOSITY AFTER STORAGE AT 50° C. SENCOR 0.5 SC(METRIBUZIN) FOLICUR 0.5 SC (TEBUCONAZOLE) PREMISE 0.5 SC (IMIDACLOPRID)0.5% 0.5% 0.5% 0.5% 0.5% 0.5% Aerosil R972 Aerosil 200 Aerosil R972Aerosil 200 Aerosil R972 Aerosil 200 (Hydro- (Hydro- 0.0% (Hydro-(Hydro- 0.0% (Hydro- (Hydro- 0.0% TEST phobic) philic) Aerosil phobic)philic) Aerosil phobic) philic) Aerosil  0 days 170 188 164 152 182 152200 235 200 21 days 224 194 174 174 176 170 210 no data 208

[0056] TABLE 4 SEDIMENTATION and REDISPERSION AFTER STORAGE FOR 21 DAYSAT 50° C. SENCOR 0.5 SC (METRIBUZIN) FOLICUR 0.5 SC (TEBUCONAZOLE)PREMISE 0.5 SC (IMIDACLOPRID) 0.5% 0.5% 0.5% 0.5% 0.5% 0.5% Aerosil R972Aerosil 200 Aerosil R972 Aerosil 200 Aerosil R972 Aerosil 200 (Hydro-(Hydro- 0.0% (Hydro- (Hydro- 0.0% (Hydro- (Hydro- 0.0% TEST phobic)philic) Aerosil phobic) philic) Aerosil phobic) philic) Aerosil Sedi-none slight slight none none slight none no data none menta- sedimentsediment sediment tion Ease of very easy w/ *easy w/ very easy w/difficult** very no data easy Redis- easy agitation agitation easyagitation easy persion

[0057] TABLE 5 PREMISE 0.5 SC WITH 0.5% TO 4.0% SILICA Spl Additive Wt 3days 10 days 14 days 21 days ID Name % TESTS @ 50° C. @ 50° C. @ 50° C.@ 50° C. A None 0.0 Viscosity 200 — — — Syneresis 30-40% 50% 60% 66%Redispersion easy easy easy easy Demarcation sharp sharp sharp sharpSediment none no tacky no tacky no tacky sediment sediment sediment BAerosil 0.5 Viscosity 224 200 — 200 Syneresis 20% 40% >60% HydrophilicRedispersion very easy very easy No further — Demarcation fuzzy/flocksharp evaluations Sediment none none performed C Aerosil 0.5 Viscosity200 210 210 — R972 Syneresis 5% 5% 10% 20% Hydrophobic Redispersion veryeasy very easy very easy very easy Demarcation indistinct sharp sharpsharp w/agglomerate Sediment none none no tacky none sediment D Aerosil0.75 Viscosity 296 — 200 Syneresis 10% >50% Hydrophilic Redispersionvery easy No further — — Demarcation fuzzy evaluations Sediment noneperformed E Aerosil 0.75 Viscosity 201 220 210 — R972 Syneresis 5% 5%10% 15% Hydrophobic Redispersion very easy very easy very easy very easyDemarcation indistinct slight flock sharp w/slight sharp w/agglomerateflock Sediment none no tacky no tacky none sediment sediment F Aerosil1.0 Viscosity 350 — 200 Syneresis 10% >50% Hydrophilic Redispersion veryeasy No further — — Demarcation fuzzy evaluations Sediment noneperformed G Aerosil 1.0 Viscosity 201 205 — — R972 Syneresis 5% 5% 5%10% Hydrophobic Redispersion very easy very easy very easy very easyDemarcation indistinct medium flock light flock sharp w/agglomerateSediment none no tacky no tacky none sediment sediment H Aerosil 2.0Viscosity 200 — R972 Syneresis 5% 6% Hydrophobic Redispersion easy veryeasy — — Demarcation sharp sharp Sediment none none I Aerosil 3.0Viscosity 230 — R972 Syneresis 2% 3% Hydrophobic Redispersion easy veryeasy — — Demarcation sharp sharp Sediment none none J Aerosil 4.0Viscosity 254 — R972 Syneresis trace 1% Hydrophobic Redispersion veryeasy very easy — — Demarcation n/a sharp Sediment none none

What is claimed is:
 1. A composition for inhibiting phase separation andresulting non-uniform distribution of an active ingredient in a lowviscosity water-based pesticide suspension, said pesticide selected fromthe group consisting of insecticides, fungicides and herbicides,comprising: a. from about 0.003% to about 50% by weight of a pesticide,excluding imidacloprid, tebuconazole and metribuzin; b. from about 0.5%to about 10% by weight of a wetting agent; c. from 0.0% to about 0.8% byweight of a thickener; d. from about 0.1% to about 0.5% by weight of anantimicrobial agent; e. from about 5% to about 20% by weight of ananti-freeze agent; f. from about 1% to about 8% by weight of anhydrophobic silica; and g. from about 40% to about 95% by weight ofwater.
 2. The composition of claim 2, wherein said pesticide is aninsecticide and wherein said insecticide is selected from the groupconsisting of chloronicotinyls and chlorothiazoles.
 3. The compositionof claim 2 wherein said insecticide is selected from the groupconsisting of thiacloprid, thiamethoxam and clothiamidin.
 4. Thecomposition of claim 1 wherein the wetting agent is selected from thegroup consisting of sodium naphthalene formaldehyde condensate andethoxylated polyoxypropylene.
 5. The composition of claim 1 wherein thethickener is selected from the group consisting of xanthan gum andhydroxypropyl methyl cellulose.
 6. The composition of claim 1 whereinthe antimicrobial agent is selected from the group consisting of1,2-benzisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one and,5-chloro-2-methyl-4-isothiazolin-3-one.
 7. The composition of claim 1wherein the antifreeze agent is selected from the group consisting ofdipropylene glycol, glycerine, hexylene glycol, and propylene glycol. 8.The composition of claim 1 wherein the hydrophobic fumed silica is ahydrophilic fumed silica treated with dimethyldichlorosilane.
 9. Thecomposition of claim 1 wherein the viscosity is less than about 900 cps.10. The composition of claim 1 wherein the pesticide comprises a friablesolid, having a melting point of less than about 60° C. and a watersolubility of no more than about 1000 ppm at about 40° C., which isresistant to Ostwald ripening and its resulting crystal growth, and isnot easily hydrolyzed or degraded by an aqueous environment.